Maleic anhydride is a readily available bulk chemical used in the manufacture of numerous chemical products, such as certain polyester resins, pesticides and preservatives. Maleic anhydride can be used as a reagent in the synthesis of dimethylmaleic anhydride (DMMA) according to the following reaction: ##STR2##
DMMA is a useful material, because it can be reacted with an aliphatic or aromatic primary amine to provide N-substituted dimethylmaleimides (DMMI) in high yield. ##STR3##
DMMIs are known to be photochemically reactive when irradiated with light of suitable wavelength, typically about 350-430 nanometers (a conventional photo-sensitizer is also often added). When photochemically reacted, the DMMIs typically dimerize in a (2+2) cyclo-addition mode to give substituted cyclobutane derivatives as illustrated in FIG. 3. ##STR4##
The R group of the DMMI molecule shown in FIG. 2 can contain a reaction site which is used in a polymerization reaction, and the polymerized material is then typically cross-linked by the photo-reaction cyclo-addition as illustrated in FIG. 3 above.
DMMI monomers are generally synthesized by reacting DMMA with a primary amino-alcohol (NH.sub.2 -R-OH wherein R can be virtually any aliphatic or aromatic group) to give an intermediate DMMI-alcohol. The DMMI-alcohol is typically esterified with methacrylic acid, or the like, and the water by-product is generally removed under azeotropic conditions as illustrated in FIG. 4. ##STR5##
The DMMI-monomer is usually copolymerized with one or more ethylenically unsaturated comonomers in solution with radical initiators such as AIBN (Azo-bisisobutyronitrile) to yield soluble DMMI-copolymers with statistical distribution of the monomer units within the macromolecule. Once the polymer backbone is synthesized, the resulting polymer typically comprises only one readily reactive functional group--the pendant DMMI groups. These groups can be dimerized or reacted together using ultra violet light (and typically also a UV sensitizer) such as is illustrated in FIG. 3, thereby cross-linking the polymers.
Such DMMI polymeric systems are generally advantageous, because the tetrasubstituted carbon-carbon double bond of the DMMI typically does not participate to any extent in the free radical polymerization reaction used to prepare the DMMI containing polymer. Most other known photosensitive functional groups will typically enter into a polymerization reaction, typically causing unwanted gelling and the like.
However, synthesizing the polymer backbone is generally not a simple reaction and is oftentimes difficult to perform on an industrial scale. Furthermore, the resulting polymer with DMMI functionality is generally not readily susceptible to variations in cross-linking, and oftentimes a more complex cross-linked network is necessary to achieve desired properties.
"DMMI-Photopolymers and Their Technical Application" by M. Roth and B. Muller, Ciba-Geigy AG, is a publication describing DMMI synthesis, DMMI polymer synthesis and cross-linking DMMI polymers by photoreacting the DMMI groups.
"A New Class Of Photopolymers With Pendant Dimethylmaleimide Groups--Part I", Die Angewandte Makromolekular Chemie 128 (1984) 71-97 by Juergen Finter, Edward Widmer, and Hans Zweifel and "A New Class Of Photopolymers With Pendant Dimethylmaleimide Groups--Part II", Die Angewandte Makromolekular Chemie 133 (1985) 147-170, by Jurgen Finter, Zeppos Haniotis, Friedrich Lohse, Kurt Meier, and Hans Zweifel, are articles which discuss and describe DMMI chemistry.
U.S. Pat. No. 4,107,174 to Baumann et al. entitled "Imidyl Compounds" is directed to photoreactive imidyl compounds, such as DMMI and is also directed to polymeric imidyl compounds which are photocross-linkable. U.S. Pat. No. 4,107,326 to Baumann et al. is also entitled "Imidyl Compounds" and is a divisional of U.S. Pat. No. 4,107,174.
None of the above-identified prior art is directed to a multifunctional diluent having more than one polymerization site and which can be advantageously used to provide a quick, simple and easy means to precisely network together diverse functional materials.